The present invention relates generally to methods and apparatus for gripping and manipulating pipe. More particularly, the present invention relates to methods and apparatus for facilitating the connection and disconnection of sections of drill pipe.
Drill strings used in rotary drilling are often constructed from individual lengths of drill pipe connected in series to form a drillstring. The individual lengths of drill pipe are commonly joined by threaded connections. Because of the loads incurred by the drillstring, the connections have to be pre-loaded with a certain amount of torque in order to maintain a satisfactory connection during use.
Pipe tongs are one tool used for facilitating the connection and disconnection, or making and breaking, of drill pipe connections. Pipe tongs are generally located at the drill floor and operate by gripping a connection between two adjacent lengths of pipe and applying torque to loosen or tighten the connection. Many pipe tongs operate by gripping above and below the junction between two adjacent pipe sections. The tongs then rotate the two sections of pipe relative to each other. This rotation often has a very limited rotational range but is performed with sufficient torque to properly make or break the connection. The torque applied to a given connection can be on the order of tens of thousands of foot-pounds.
Because of the high torque loads applied to the pipe, pipe tongs have been known to scar the outer diameter of the pipe, especially if the pipe slips within the tong. In order to minimize this slippage, as well as to ensure the proper torque requirements are met, the interface between the pipe and the tong is critical. In some cases, pipe tongs have been known to partially collapse the pipe with an excessive clamping force. Excessive damage to the pipe is often a result of the pipe not being centered within the pipe tong causing the gripping mechanism of the tong to apply uneven force to the pipe.
Thus, there remains a need to develop methods and apparatus for facilitating the connection and disconnection of pipe sections, which overcome some of the foregoing difficulties while providing more advantageous overall results.